1. Field of the Invention
The present invention relates to deep sea mining apparatus for recovering minerals from the ocean floor, and more particularly to deep sea mining apparatus wherein a high velocity water jet is provided to cause an upward flow through a dredge pipe of nodular materials found on the ocean floor.
2. Description of the Prior Art
Within the past 25 years or so, it has been discovered that the sea bed contains a large quantity of metallic and mineral materials, some of which are in the form of nodules that are of irregular shape and resemble potatoes in size and shape. A particularly high concentration of such nodules is found in the east-central Pacific Ocean at depths of approximately 15,000 feet. Such nodules have a high percentage of valuable metals, such as nickel, cobalt, manganese, and copper. For example, nodules have been found in that are that have approximately 1.3% nickel, approximately 1.1% copper, approximately 0.2% cobalt, and approximately 25% manganese. It is estimated that by utilizing ocean mining of such nodules, the United States could become self sufficient with respect to its needs for both cobalt and manganese, rather than having to import over 90% of those materials as at present, and that it could be self sufficient to the extent of meeting from about 70% to about 90% of its current needs for nickel and copper. Thus there is substantial economic interest in utilizing deep sea mining to obtain the benefits of the vast untapped resources in the sea of the metals identified above.
Previously-disclosed technqiues for obtaining manganese nodules from the ocean floor have involved the use of compressed air or compressed gas for generating a flow of water in a pipe to draw the nodules upwardly from the ocean floor to a suitable mining ship. For example, in U.S. Pat. No. 3,456,371, which issued on July 22, 1969, to J. R. Graham et al, there is disclosed a remotely controlled gathering vehicle, or tractor, having scraper blades and a collector head. The gathering vehicle is remotely controlled from a mining ship and traverses the ocean floor to gether and collect manganese nodules. The disclosed apparatus includes a source of compressed air, which is injected into a dredge pipe at a point below the surface of the ocean to generate an upward flow of water within the pipe.
U.S. Pat. No. 3,765,727, which issued Oct. 16, 1973, to Joseph G. Santangelo et al, discloses a deep sea mining apparatus that also utilizes the injection of compressed air into a dredge conduit to cause an upward flow of water in the conduit. A submerged nozzle is provided adjacent the ocean floor, and is connected to a suitable dredge pipe that is in communication with the mining vessel. The compressed air is introduced at a point below the surface of the water in order to induce an upward flow in the dredge pipe.
U.S. Pat. No. 3,971,593, which issued July 27, 1976, to Robert Porte et al, shows a deep sea mining apparatus wherein a movable collecting vehicle is provided that moves along the sea floor. A submerged underwater station is in communication with the collecting vehicle and includes a power unit and a storage zone for collected nodules. The underwater station also includes means for providing a compressed gas that is forced into the dredge pipe, again to induce an upward flow therein of material from the ocean floor.
The deep seam mining technique disclosed in the above-identified patents each involve the injection of a compressed gas into a dredge pipe. Thus suitable gas compression apparatus is required. However, the use of compressed gas complicates the mining process because the lifting pipe is subjected to three different materials--gas, water, and manganese nodules and other solids, all of which can cause process instability. Additionally, a large diameter dredge pipe is required, and the pipe must increase in diameter as the surface of the water is approached to permit expansion of the air as it approaches the surface. It is therefore desirable to provide an apparatus that does not require a large diameter dredge pipe that increases in diameter by tapering outwardly in an upward direction.